Starting with Chef Client 12.11, there is support for the consistent, standard exit codes as defined in Chef RFC 062.
With no additional configuration when Chef Client exits with a non-standard exit code a deprecation warning will be issued advising users of the upcoming change in behavior.
To enable the standardized exit code behavior, there is a new setting in client.rb. The exit_status setting, when set to :enabled will enforce standarized exit codes. In a future release, this will become the default behavior.
If you need to maintain the previous exit code behavior to support your current workflow, you can disable this (and the deprecation warnings) by setting exit_status to :disabled.